VALVE OPERATING GEAR

Abstract: A valve operating system for an internal combustion engine (1), which includes a cam shaft (8) actuated floating lever (40) having a cam surface (41) acting on a push rod (18) of a valve assembly (5), the position of the push rod (18) on the cam surface (41) being varied by a lever arm (22) acting on a sliding bearing (23) on the push rod (18) to change the degree of lift or timing of the valve assembly (5). The other end of the floating lever (40) may be supported by a further cam shaft (44), hydraulic lifter or sliding pivot.

Description: VALVE OPERATING GEAR TECHNICAL FIELD This invention relates to a valve operating gear, more particularly to a valve operating gear or valve train for an internal combustion engine, and to an internal combustion engine having such a valve system. BACKGROUND ART Due to the diminishing oil reserves, and also the necessity for internal combustion engines to be less polluting, various developments have been made in the design of internal combustion engines to improve their efficiency. One development has been to include a mechanism for varying the timing and the degree of opening of either or both the inlet and exhaust valves. Internal combustion engines are required to operate at a range of speeds from idle to high revolutions. Hence valve arrangements on internal combustion engines must be able to act over that wide range of engine speeds. It only possible however, in a normal engine to optimise the valve settings for a particular engine speed and hence the valves may open too much or be opened for too long at low engine speeds and not have enough lift or not be open long enough at high engine speeds. Hence an internal combustion engine needs a throttle valve in an air inlet to reduce the air intake to a cylinder at idle. If an inlet valve opened less then a throttle may not be needed. It may also be noted that at high engine revolutions it is desirable to hold open an exhaust valve after to dead centre to induce some hot gases from the exhaust to return into the valve to heat the inlet fuel mixture before combustion. If valves are set to have this occur at all engine speeds then the engine will not work properly at low engine speeds. At low engine speeds such an arrangement will not work and therefore it is desirable to have a valve system which can provide for different lift and timing at high and low engine speeds. One method by which control of engine timing and lift is achieved has been disclosed in Australian Patent Specification Number 615420 where the variation is achieved by the use of a second cam shaft operating a further hydraulic tappet which hydraulically modifies the action of the main hydraulic tappet to vary the valve operation. Another method of varying valve timing is shown in United States Patent Number 5027760. This patent shows an arrangement whereby a finger of varying width can be inserted between a cam and an end of a valve shaft so as to vary the timing and valve opening at different speeds. This arrangement is only suitable for overhead valve engines. British Patent Number GB 2200952 disclosed a method of varying valve timing and lift by use of dual cams and rockers and varying the effect each or both have onto the valve at various engine speeds. This requires at least a four valve engine which can be quite expensive. A dual valve system is also provided in United States Patent Number 5036807 with one valve for low speed operation and another valve for high speed operation. This arrangement uses engine oil pressure as an indication of engine rotational speed and hence as engine speed increases and oil pressure increases the high speed valve is actuated. It is the object of this invention to provide an alternative arrangement of an internal combustion engine with variable valve lift and timing which will overcome at least some of the above problems. It is an alternative object to at least provide the public with a useful alternative. BRIEF DESCRIPTION OF THE INVENTION In one form therefore, the invention is said to reside in a valve operating system for an internal combustion engine, the mechanism including a cam shaft, a push rod, a valve rocker and a valve assembly actuated by the valve rocker characterised by a floating lever actuated by the cam shaft with the floating lever having an arcuate surface forming a cam surface, the push rod being actuated by the cam surface and means to vary the position of the push rod on the cam surface to thereby vary the operation of the valve associated with the push rod. In a preferred form of the invention the floating lever is supported for rotation at one end thereof and the cam shaft acts on the other end thereof and the cam surface is between the one end and the other end. Preferably the floating lever is supported for rotation at the one end thereof by means of an hydraulic lifter, the hydraulic lifter adapted to support the one end during the period that the cam shaft acts upon the floating lever. Preferably the means to vary the position of the push rod includes an arm mounted to a sliding block on the push rod, the arm being adapted to be moved longitudinally to vary to position of the push rod on the cam surface. The arm may be adapted to be moved longitudinally by means of an hydraulic ram. Alternatively the arm may be adapted to be moved longitudinally by means of a crank arrangement. In an alternative form of the invention, there may be further included a pivot shaft mounted adjacent to, and adapted to rotate at the same speed, as the cam shaft, the pivot shaft having a plurality of cams thereon each cam on the pivot shaft adapted to support a respective floating lever during the period that the cam shaft acts upon the floating lever. There may be provided spring means to hold the floating lever off its cam on the pivot shaft and against the end of the push rod. In a preferred form the push rod may include a support sleeve, the support sleeve including support bearings at upper and lower ends thereof and the means to vary the position of the push rod on the cam surface acting onto the support sleeve. In one preferred form the arcuate surface forming the cam surface may have a radius of curvature equivalent to the length of the push rod. Alternatively the arcuate surface forming the cam surface may have a non-radius surface so as to provide prolonged opening and/or greater lift to a valve of the valve assembly at higher engine speeds. This is particularly useful for exhaust valves. In an alternative form the invention may be said to reside in a push rod operated valve of an internal combustion engine, the push rod being actuated by cam surface on a lever, the lever being oscillated to actuate the push rod, whereby on varying the position of the push rod on the cam surface the operation of the valve is varied on timing and/or lift. In an alternative form the invention is said to reside in an internal combustion engine including a plurality of pistons reciprocating in respective cylinders, each cylinder having at least one inlet valve assembly and at least one exhaust valve assembly, a cam shaft driven by the engine having a plurality of cams thereon each cam adapted to activate a respective valve assembly, characterised by a lever arrangement between each cam and the valve assembly and upon which the cam operates whereby the degree of lift provided by the cam can be varied by variation of the position of a push rod of the valve assembly on the lever with respect to the fulcrum of the lever arrangement. This embodiment may further include a pivot shaft adapted to be driven at the same rotational speed as the cam shaft, the pivot shaft having a plurality of cam lobes thereon each cam lobe being adapted to provide the fulcrum of the lever arrangement during the time that the cam operates on the lever. The position of the push rod on the lever arrangement may be adapted to be between the fulcrum and the point at which the cam operates. Preferably there may be means to vary the position the push rod in response to engine demand parameters. Hence it will be seen that by this invention there is provided an internal combustion engine which allows for variation in lift and timing of valve opening. At low speeds it allows for elimination of a throttle valve in an air inlet and if necessary the lift can be stopped altogether to give engine braking or compression or exhaust braking. At higher speeds is allows valves to open longer to induce a better charge and more fuel to allow clearance of exhaust gases and better combustion. The pivot shaft does not itself lift the valve but takes pressure off the push rod when opening is not needed. The actuation of the arm to srnry the position of the push rod on the cam surface of the lever can be automatic and can be controlled directly by an engine parameter such as speed or can be manually operated. Operation of the variation of pivot arm position may be the same for all inlet and exhaust valves respectively of an valve train or it may be independent for each valve or cylinder. The operation of the valve can be varied from no lift at the pivot end of the cam surface to full lift at just the pivot side of the lifting cam. The invention can thus eliminate the need of a throttle valve which causes vacuuming in the inlet manifold stopping flow into the cylinders. Another advantage of the present invention is that it may enable various cylinders of a multi-cylinder engine to be operated differently. Hence a six cylinder engine could be set up such that at times of low power draw three of the cylinders could have their valves closed off completely or their inlet valves closed and their exhaust valves opened during both compression strokes so that less fuel is used and load on the engine is reduced. This then generally describes the invention but to assist with understanding of the invention reference will now be made the accompanying drawings which show a preferred embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows in schematic view of an internal combustion engine with one embodiment of the present invention. FIG. 2 shows an alternative view of an internal combustion engine with an alternative embodiment of the invention. FIG. 3 shows a schematic view of an internal combustion engine including a further embodiment of the present invention. FIG. 4 shows part of the embodiment shown in FIG 3 with the cam shaft rotated through 90°. FIG 5 shows a side view of part of the pivot shaft of one embodiment of the present invention. FIG 6 shows a push rod support arrangement according to one embodiment of the invention. FIG 7 shows one embodiment of an arrangement for varying the position of the push rod on the lever arm. FIG 8 shown an alternative embodiment of lever arm according to this invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Looking at FIG. 1 it will be seen that there is an internal combustion engine 1 including a cylinder 2 in which a piston 3 is adapted to reciprocate on a crank shaft 4. A valve assembly generally shown as 5 opens a valve 6 for an inlet or exhaust outlet 7. A cam shaft 8 includes a cam lobe 9 which acts upon a cam follower 10. The cam follower 10 includes a socket 11 into which fits a ball 12 mounted onto a lever arm 13 which is adapted to pivot about a pivot point 14 which is fixed on a solid portion 15 of the engine. The slot 27 in the lever arm 13 allows for transverse movement of the lever 13 as the cam lobe 9 lifts the lever arm 13. The lever arm 13 includes a arcuate surface 16 upon which is supported the end 17 of a push rod 18. The push rod actuates the valve assembly 5 through a ball 19 and socket 20 on the valve assembly. The position of the push rod end 17 on the cam surface 16 can be varied by means of lever arm 22 acting onto a sliding bearing 23 on the push rod. A crank arrangement 24 is adapted to be rotated to move the position of the push rod on the cam surface. The crank arrangement 24 can be rotated by means not shown to provide this variation in position. At low engine speeds the crank arrangement 24 is moved so that the push rod end 17 is at the end 25 of the cam surface and at high engine revolutions the push rod end 17 is moved to the end 26 of the cam surface. It will be realised for full valve closing and for allowance for thermal expansion and contraction a gap must be left between the cam surface 16 and the end of the push rod 17. FIG 2 she - an alternative embodiment which provides a different support for i ie lever i angement. In this drawing the same reference numerals are used as in FIG 1 for the same components. The support for the pivot end generally shown as 30 of the lever arrangement is provided by means of a ball 31 supported on a socket 32 which in turn is supported by a piston 33 in a hydraulic cylinder 34. A spring 35 biases the piston upwards so that the ball 31 an socket 32 are together and the cam surface 16 engages the end 17 of the push rod 18. When no load exists on the piston 33 from the ball 31 the spring 35 moves the piston 33 upwards eliminating clearance between the bal 31 and socket 32. This action sucks oil into the cylinder 34 past the ball valve 37 against the action of spring 38 which is supported in cage 39 on the bottom of the piston 33. The piston 33 is designed so that a slight leakage of oil during the loaded phase of its operation assures valve closure.. The leakage of oil is replaced during the period of no load as discussed above. Supply of engine oil under pressure through tube 36 comes from oil supply systems of an engine and the arrangement operates in the same manner as an hydraulic valve lifter does. The hydraulic cylinder 34 may be a slave cylinder acting from a master cylinder. This would enable one or more cylinders to be deactivated if less power was required. FIG 3 shows an alternative arrangement for support of the lever arrangement 16. In this embodiment the lever 40 has a cam surface 41 which has a radius of curvature in the direction along which the end 19 of the push rod 18 acts which is the distance between the cam surface 41 and the centre of rotation of the ball 19 in the socket 20. Below the lever arm is a pivot shaft 44 which includes a number of cams 45 and is supported for rotation in a housing 46 on bearings which will be seen in more detail in respect of FIG 5. The pivot shaft 44 is driven so as to rotate at the same rotational speed as the cam shaft 8 and the lobe 47 on the pivot shaft 44 is so positioned for each cam on the cam shaft 9 that it acts onto the protrusion 42 on the lever arm 40 at the same time as the lobe 9 on the cam shaft 8 acts onto the cam follower 10. A spring 48 holds the lever 40 off the cam surface 45 and against the end 17 of the push rod 18. As can be seen in FIG 4 when the cam shaft 8 has rotated so that the lobe 9 is fully engaging the can follower 10 and the lever 40 has been lifted to thereby lift the push rod 18 the lobe 47 on the pivot shaft 44 is also engaging the protrusion 42 on the lever arm 40. This provides the fulcrum for rotation of the lever 40 during lifting of the pushrod 18 and hence actuation of the valve assembly 5. It will be noted that the fulcrum is provided during that period when the lobe 9 is interacting with the cam follower 10. In a preferred embodiment of the invention the lobe 45 of the pivot shaft 44 commences engagement with the protrusion 42 about 85° before full engagement of the lobe 9 on the cam follower 10 and fully supports the lever at about 30° before full engagement and supports it for at least 30° afterwards and final disengagement comes some 85° afterwards. By this arrangement clearance does not have to be provided in the valve assembly or between the end 17 of the push rod and the arcuate surface 41 and hence a quieter arrangement is provided in an engine. FIG 5 shows an alternative view of the pivot shaft 44 in its housing 46. There are three push rods 18 shown with their ends 17 in the form of a yoke straddling the lever 40 and the protrusion 42 just engaging the tip of the cam 47. Bearings 49 between the pivot shaft 44 and the housing 46 are provided at intervals along the pivot shaft to support the pivot shaft. Recesses 50 are cut into the housing 46 at intervals to enable the lever to engage the cam lobes 45 on the pivot shaft 44. FIG 6 shows an alternative embodiment of a support arrangement for a push rod of the valve assembly. The push rod 60 is surrounded by a support tube 61 with caps 62 at each end including apertures through which the push rod 60 moves. A push rod support bracket 63 mounted to the engine block or cylinder head 64 bears against the cap 62 and holds the support tube 61 in place. A spring 69 holds the support tube 61 against the support bracket 63. The lever arm 65 is mounted by means of a yoke having a pivot 66 to the support tube so that the support tube and push rod can be moved along the cam surface 67 with the end of the push rod 68 onto the cam surface 67. By this arrangement where the push rod 60 is supported so that forces around its middle portion do not occur then flexing of the push rod and hence mistiming will not occur. FIG 7 shows an alternative arrangement by which the position of the push rod can be varied on the cam surface. In this embodiment the housing 46 of the pivot shaft 44 has an annular sleeve 70 fitted around it and adapted to rotate on it. The sleeve 70 includes an arcuate toothed portion 71 which engages with another arcuate tooth portion 72 adapted to pivot about point 73. Movement of the lever 74 which actuates the toothed sector 72 about the pivot point 73 will cause rotation of the sleeve 70 by means of the inter-engaging gear teeth. Also on the sleeve 70 is a shift handle 78 which is connected onto connector arm 79 which in turn engages the support tube 80 on the push rod 81. It will be realised that the connector arm 79 could include a yoke to fit over and mount to the support tube for the push rod as depicted in FIG 6. FIG 8 shows an alternative embodiment of lever arrangement of the type shown in Figures 3 and 4. The lever arrangement 90 has a ball 91 adapted to be supported in the socket 11 of a cam follower 10 and includes a protrusion 92 to act against the lobe 45 of the pivot shaft 44 as depicted in FIG 3. The upper arcuate surface, however, is not of a radius of curvature equivalent to the length of the push rod which is shown by the dotted line 94 in FIG 8 but is of a curve so that at the end 95 which is used for low speed or idle operation it starts at the same radius of curvature but at the end 96 which is used for high speed operation the distance between the arcuate surface and the socket 20 of the valve assembly is such as to increase the time the valve is opened by opening the valve earlier and closing the valve later. This arrangement is particularly useful for exhaust valves where it is desirable to hold such exhaust valves open longer and/or wider during the exhaust phase of the operation of the internal combustion engine. When the push rod is in the non- lift position 95 the position of the lever may be set so that the protrusion 92 bears against the back of the cam 45 while the surface 93 is against the end of the push rod. When the push rod is swung towards the end 96 the gap between the pivot shaft 4 and the lever arm protrusion 92 is lessened and closing of the valve is prolonged. A similar effect can be obtained by if the radius of the lever arm is cut with the lever in a horizontal position and then adjusted in an upward position. Closing of the gap between the non-supporting section of the pivot shaft and the protrusion on the lever arm when the cam lobe is not lifting the lever arm will provide a prolonging of the closing of a valve. Thus it will be seen that there is provided according to this invention a means whereby the timing and/or lift of a valve of an internal combustion engine can be varied. This control can be applied to either or both of the inlet and exhaust valves. It will be realised that the inlet valves will have to have a separate control system from the exhaust valves for the most effective and efficient operation. Exhaust and inlet valves could operate together with the same push rod setting but not necessarily with the same opening settings. The exhaust valve could open further and slightly ahead of the inlet valve .

Claims: CLAIMS 1. A valve operating system for an internal combustion engine, the mechanism including a cam shaft, a push rod, a valve rocker and a valve assembly actuated by the valve rocker, characterised by a floating lever actuated by said cam shaft with the floating lever having an arcuate surface forming a cam surface, the push rod being actuated by the cam surface, and means to vary the position of the push rod on the cam surface to thereby vary the operation of the valve associated with the push rod. 2. A valve operating system as in Claim 1 wherein the floating lever is supported for rotation at one end thereof and the cam shaft acts on the other end thereof and the cam surface is between the one end and the other end. 3. A valve operating system as in Claim 2 wherein the floating lever is supported for rotation at the one end thereof by means of an hydraulic lifter, the hydraulic lifter adapted to support the one end during the period that the cam shaft acts upon the floating lever. 4. A valve operating system as in Claim 1 wherein the means to vary the position of the push rod includes an arm mounted to a sliding block on the push rod, the arm being adapted to be moved longitudinally to vary the position push rod on the cam surface. 5. A valve operating system as in Claim 4 wherein the arm is adapted to be moved longitudinally by means of an hydraulic ram. 6. A valve operating system as in Claim 4 wherein the arm is adapted to be moved longitudinally by means of a crank arrangement. 7. A valve operating system as in Claim 1 further including a pivot shaft mounted adjacent to and adapted to rotate at the same speed as the cam shaft, the pivot shaft having a plurality of cams thereon, each cam on the pivot shaft adapted to support a respective floating lever during the period that the cam shaft acts upon the floating lever. 8. A valve operating system as in Claim 7 further including spring means to hold the floating lever off its cam on the pivot shaft and against the end of the push rod. 9. A valve operating system as in Claim 1 wherein the push rod includes a support sleeve the support sleeve including support bearings at upper and lower ends thereof, and the means to vary the position of the push rod on said cam surface acting onto the support sleeve. 10. A valve operating system as in Claim 1 wherein the arcuate surface forming the cam surface has a radius of curvature equivalent to the length of the push rod. 11. A valve operating system as in Claim 1 wherein the arcuate surface forming the cam surface has a non-radius surface so as to provide greater lift to a valve of the valve assembly at higher engine speeds. 12. A push rod operated valve of an internal combustion engine, the push rod being actuated by a cam surface on a lever, the lever being adapted to be oscillated to actuate the push rod, whereby on varying the position of the pushrod on the cam surface the operation of the valve is varied in timing and/or lift. 13. An internal combustion engine including a plurality of pistons reciprocating in respective cylinders, each cylinder having at least one inlet valve assembly and at least one exhaust valve assembly and a cam shaft driven by the engine having a plurality of cams thereon, each cam adapted to actuate a respective valve assembly, characterised by a lever arrangement between each cam and valve assembly upon which the cam operates whereby the degree of lift provided by the cam can be varied by variation of the position of a push rod of the valve assembly on the lever with respect to a fulcrum of the lever arrangement. 14. An internal combustion engine as in Claim 13 further including a pivot shaft adapted to be driven at the same rotational speed as the cam shaft, the pivot shaft having a plurality of cam lobes thereon each cam lobe being adapted to provided the fulcrum of the lever arrangement during the time that the cam operates on the lever. 15. An internal combustion engine as in Claim 13 wherein the position of the push rod on the lever arrangement is adapted to be between the fulcrum and the point at which the cam operates. 16. An internal combustion engine as in Claim 15 further including means to vary the position of the push rod in respect to engine demand parameters.

Inventors: WRIDE DONALD CHARLES, WRIDE, DONALD, CHARLES
Applicants: WRIDE DONALD CHARLES, WRIDE, DONALD, CHARLES
Application year: 1994
Main classification: F01L1
IPC codes: F01L13